1. Field of the Invention
The present invention relates to a medical image alignment apparatus, method, and program for determining positional correspondence relationship between a plurality of three-dimensional images which include vertebrae. The invention also relates to a cross-sectional spine image display apparatus, method, and program, and more particularly to a cross-sectional spine image display apparatus, method, and program for generating a cross-sectional image of a vertebra portion based on three-dimensional image data and displaying the generated image.
2. Description of the Related Art
When performing comparative image reading of a plurality of three-dimensional images formed of a plurality of cross-sectional images sliced in a direction orthogonal to a body axis direction, there is a demand for displaying corresponding cross-sectional images of each three-dimensional image side by side by performing site recognition and determining correspondence relationship between each cross-sectional image in each three-dimensional image based on a pair of corresponding slice positions specified by the operator, a slice thickness of each three-dimensional image, and the like.
In response to such a demand, it is conceivable that the same region may be extracted from a plurality of three-dimensional images formed of a plurality of cross-sectional images using a technology, such as that described in Japanese Unexamined Patent Publication No. 2008-006187, which recognizes an anatomical structure included in a medical image and displays an axial image of the specified region based on information of the recognized region.
In the mean time, with the recent progress in imaging devices (modalities), resolution of image data obtained by imaging devices has improved, thereby allowing detailed analysis of a subject based on the image data. For example, the multi-detector row computed tomography may obtain a plurality of tomographic images at a time, and tomographic images with a thin slice thickness may be obtained. A thinner slice thickness results in improvement in the resolution of three-dimensional data, in a body axis direction, made up of a plurality of stacked tomographic images, whereby more detailed three-dimensional image data may be obtained.
A structural analysis of a vertebra may be performed using the aforementioned three-dimensional data. For example, Japanese Unexamined Patent Publication No. 2009-207727 describes that a center line of a vertebra is obtained by analyzing three-dimensional image data. Japanese Unexamined Patent Publication No. 2009-207727 also describes that a spongy portion of each vertebral body constituting a vertebra in a body axis direction is estimated based on pixel values (voxel values) of a specific region near the center line of the vertebra, then a characteristic amount of pixel value of the specific region is calculated in estimated spongy portion of each vertebral body, a three-dimensional center of the cavernous portion of each vertebral body is detected based on the characteristic amount, and positions of both ends of each vertebral body are calculated based on the detected three-dimensional center. Further, Japanese Unexamined Patent Publication No. 2009-207727 describes that a midpoint between three-dimensional centers in spongy portions of adjacent two vertebral bodies is determined to be the intervertebral portion of the two vertebral bodies.
Use of the method described in Japanese Unexamined Patent Publication No. 2008-006187 allows recognition of which of head region, neck region, chest region, abdominal region, and leg region is represented by which of sliced images and, therefore, it is possible, for example, to extract chest axial images from a plurality of three-dimensional images. But, it is difficult to extract axial images at precisely corresponding chest positions.
Further, use of the method described in Japanese Unexamined Patent Publication No. 2008-006187 allows alignment only in a body axis direction as the method performs alignment using tomographic images orthogonal to the body axis direction. For example, the aforementioned method may not respond to the demand for performing comparative image reading with respect to a cross-section orthogonal to the center line of a specific vertebra in a past three-dimensional image and a cross-section at a corresponding position in a current three-dimensional image, as required in the examination of vertebral problems.
The present invention has been developed in view of the circumstances described above, and it is an object of the present invention to provide a medical image alignment apparatus, method, and program capable of automatically determining positional correspondence relationship between a plurality of three-dimensional medical images with high accuracy.
Further, for example, in the field of orthopedic surgery, there may be a case in which each vertical cross-section of a spine is displayed and observed using three-dimensional image data. In the display of the vertical cross-section of spine, it is conceivable that a cross-sectional image of a vertebra sliced orthogonal to the center line at the position of each vertebral disc is generated and a plurality of cross-sectional image is displayed side by side. But a region desired to be observed does not always correspond to the position of the vertebral disc displayed in cross-section. There may be a case in which the observer, such as a doctor or the like, wants to move the position of the cross-sectional image to be displayed from the position of the cross-sectional image currently displayed. But, in the display of vertebrae in cross-section, there has been no such function to adjust positions of cross-sections, and it has been possible to display only a cross-section at a fixed position.
In view of the circumstances described above, it is a further object of the present invention to provide a cross-sectional spine image display apparatus, method, and program that allows an observer to easily observe a cross-section at any position in the cross-sectional display of vertebrae.